DynamicTablesPkg: Add SSDT Serial port for DBG2

DynamicTablesPkg: Add SSDT Serial port for DBG2

The SSDT Serial port fixup library provides
interfaces to generate a SSDT Serial port table
based on the serial port information.

Update the DBG2 Generator to use the SSDT serial
port fixup library to build a serial port definition
block for the DBG2 serial port and install the
SSDT table.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>